Never heard of that before, could you explain what is involved and the reason it works? Obviously it's not a possibility for me now but it sounds interesting.
I think the biggest failure in tank startup is due an assumption by hobbyists that just because a plant is aquatic, then this automatically means that the plant can adapt immediately to live under water or that the plant prefers to be submerged There are only a handful of plants that live 100% of the time in water. For half the year, normally in the dry season, the aquatic plant is dry and lives like any typical terrestrial plant. The leaf structure during this time is adapted to being suspended in air. The movement of CO2 and other gases such as oxygen is through the pores (stomata) on the leaf. These are basically ventilation holes. When the wind blows, like a flute, the pressure differences across these stomata facilitate movement of the gases through the leaf. Look at the cross sectional diagram here:
Terrestrial leaves are built to protect itself from bacteria, pests and water intrusion. Look at the image and note that the outermost layers of the leaf are coated with something called a cuticle, which is basically the "fingernail" of the leaf. This is a hard, water repellent, waxy substance that gives leaves that shiny appearance.
So imagine that I now take this leaf and dunk it under water. Do you think this mechanism can still work effectively as it did in air? Those air spaces, where critical gas exchange occurs so easily in air get flooded. CO2, Oxygen and other gasses move 10,000 time more slowly in water than they do in air. The leaf literally drowns. The plant has to make a new leaf structure that works in water, not in air.
Haven't you ever noticed that the shape and appearance of a submersed plant is entirely different than when you buy it from the nursery? The submersed leaves are spongy, slippery and flaccid, dries out and crumbles easily if left too long out of water. In submersed leaves the composition of the cuticle
has to change. It has to allow more water and gas to penetrate, so it either becomes much thinner, becomes less hydrophobic, or disappears entirely. This allows gases and nutrients to move directly to the sites that use them instead of depending solely on the vascular transport mechanisms.
In natural habitats, when the rainy season starts, the flood waters rise relatively slowly. This gives the plant time to trigger the changes while still allowing them to breathe through the upper leaves. The stems elongate to keep the upper leaves out of the water as long as possible while the areas that are submerged start to grow new leaf structure.
The temperature falls. Gasses dissolve better as the water is cooler.
The water gets cloudy or murky. This reduces the PAR where the new leaves are growing and reduces their requirement for CO2 uptake.
The Matrix programs us to dump plants in water, to avoid feeding nutrients and to zap them immediately with megawattage. Do you still think this is wise?
When you float the plants it helps to trigger the change to a submersed form while still allowing some leaves to breathe. In a way, it's like handing them a snorkel.
You can still do all these small things to help new arrivals as well as during start up. Reduce the lighting for a few weeks, lower the temperature and float some plants. Of course it's not practical for some plants like carpet plants or mosses, which are difficult enough to get them rooted in the substrate, but it is very helpful for difficult plants.
Cheers,